A reflex test of the knee is the basis for the term knee-jerk reaction.. A knee-jerk reaction is typically impulsive in nature and doesn't allow for someone to think things through. An outburst of anger is an example of a knee-jerk reaction.
As Figure 1 shows, the central processing unit consists of two parts: The control unit and the arithmetic/logic unit. Each part has a specific function. Before we discuss the control unit and the arithmetic/logic unit in detail, we need to consider data storage and its relationship to the central processing unit.
This is where everything comes together to work. The system box holds the central processing unit to act as the brains of the computer. The unit contains the motherboard which is the main circuitry for the system. The power supply for the main computer is located in the unit. All the other parts including the monitor, mouse, keyboard, speakers, and others join at the unit to become a functional system.